I've got a 1/4" thick piece of O-1 to work with. Is that too thick? I've never made a knife before so this is my first try. Do I need to do anything special to it before I cut out my blade?

read on story about magical swords in category stories...it may help

I forgot to mention that I'll be trying to use the stock removal method...any tips?

inter library loan. get all the books you can lay your hands on read them and then take a whack at your project. It is a good solid way to get needed information.
Finnr

Yes it's too thick; No it's not thick enough---depends on your design which I seemed to have missed in your post.

Also it can depend on your tooling---a 2hp Bader with a coarse belt can work too thick to too thin in about the time it takes to say "OOPS!".
A file can take days just to get it down to size.

i have done alot of knives with just a canadian tire 4" grinder. it can be used to cut to rough shape with thin cut-off blades, then grinding discs for the actual blade bevel and more detailed shape, then a sanding wheel to take out the grind marks. you have to be very careful of overheating (i just let a hose dribble water on it the whole time) and be careful of how much you grind off. try to keep your wheel as flat to the steel as possible so that it doesn't "bite" the steel. that makes it look horrible. after the sanding disc i usually take my pad sander at 80 then 120 grit to the blade which cleans it up nicely for buffing or if you're careful it can leave a cool pattern on the blade.